The international standard IEC61375 divides a train communication network (TCN) into two hierarchical networks, namely a train backbone network at a higher level and consist networks (CNs) at a lower level. Currently, the train backbone network is mainly based on bus technology, and consists, for example, of wire train bus (WTB) and multifunction vehicle bus (MVB). WTB is primarily used in vehicles such as locomotives and EMU trains having requirements for dynamic car configuration, and MVB is primarily used in vehicles such as EMU trains with fixed car configuration.
The process for initiation and dynamic configuration of TCN is called train inauguration. The inauguration process is a precondition for normal operation of TCN and is performed when power supply or car configuration in a train changes. This process involves assignment of identifiers (IDs) to train backbone nodes (TBNs) and CNs, construction of physical topology for the network, determination of direction of cars with relation to a reference direction of the backbone network, and construction of logical topology for the network, etc.
Because a train backbone network consists of linear networks, completion of communications in such a network critically depends on topology discovery or train inauguration. Topology discovery or train inauguration is, however, achieved through learning and exchange of messages among BNs in the network. According to current standard for inauguration of wired train backbone networks, only neighboring BNs are connected via physical wires (as shown in FIG. 1). Therefore, train backbone communications can also be achieved by establishment of wireless communication link between two neighboring BNs belonging to different CNs (as shown in FIG. 2). Compared with wired communications, wireless communications are more flexible and convenient, and can solve problems such as difficulty of wire connections between consist networks in a wired backbone network, lack of wiring space, complexity in operation and maintenance, and so on. However, the implementation of topology discovery over a wireless network is made difficult by the broadcast nature of the wireless medium, and by fading and interference.
To summarize, the implementation of topology discovery over a wired network is capable of realizing train inauguration, but is restricted in its application by electrical connections between cars, high wiring cost, difficulty in detecting of a line fault and in maintaining of lines, limited wiring space for which it has to contend with power lines, and by the need to manually cut off or reconnect the cables between different consist networks for car reconfiguration, which is complex to operate and time-consuming, and may result in wrong and unstable cable connection. Besides, connectors used become easily aged and may also cause faults in the lines.
Backbone communications based on a wireless network can avoid all the above problems. However, the implementation of wireless topology discovery is made difficult by the broadcast nature of the wireless medium, and by fading and interference.
It is therefore desirable to provide a method and a system for simple and effective topology discovery for a wireless train backbone network, for example, in the process of train inauguration.